Advertisement
Summary: The study shows how stress can induce sleep in mice and how this stress-induced sleep can help reduce anxiety the next day.
Source: Imperial College London
Stress promotes a type of sleep in mice that subsequently relieves anxiety, according to new research that also reveals the mechanism responsible.
Since sleep is similar in mammals, it is likely that the same mechanism is triggered in the human brain. Uncovering the mechanism could lead to artificial ways to amplify its effects and help treat persistent stress disorders like PTSD.
We often think of stress as keeping us up at night, but certain types of stress actually seem to induce sleep. Now a study led by researchers from Imperial College London and institutions in China has uncovered how this happens in the brains of mice.
Not only did they discover how sleep is induced, but they also reported that allowing the mice to sleep seemed to lower their anxiety levels the next day. The results are published in the journal today Science.
There are two main types of sleep that we and all mammals experience: REM (rapid eye movement, during which we tend to dream) and non-REM (NREM; deeper, dreamless sleep). People suffering from PTSD experience less REM sleep, contributing to the theory that REM sleep helps us process difficult emotions and stress.
Lead researcher Professor Bill Wisden of the Department of Life Sciences at Imperial said: “Our findings reinforce the idea that REM sleep helps us manage stress. However, until now we only knew how REM sleep is reduced, such as: B. some drugs that suppress it.
“Now, our study has revealed a mechanism by which REM sleep is induced, paving the way for drugs or other interventions that target the right neurons and increase the stress-relieving power of sleep.”
The researchers induced a type of psychosocial stress in mice called “social defeat,” which is used as an analogue of bullying in humans. Mice were exposed to particularly aggressive mice (without physical harm), after which the researchers found that “flight or fight” hormones rose in their blood, indicating stress.
Then, when the mice slept, the researchers tracked the activity of their neurons (brain cells). This revealed a specific group of neurons that sensed and responded to stress hormone levels and induced high levels of sleep in both NREM and REM.
The activity of these neurons and NREM and REM sleep levels stayed high for about five hours of sleep, during which time they also sent signals to other neurons that regulate stress hormones, preventing them from releasing more.
The newly discovered nerve cells not only recognized stress and thereby triggered sleep, they also triggered the reduction of stress hormones.
As soon as the mice woke up, the researchers tested their fear response to see how sleep had affected their stressful behavior. They did this by measuring how long the mice spent in the light rather than seeking the dark, as they tend to do more when they are anxious.
Their responses were compared to stressed mice that were either sleep-deprived (stimulated with objects) or whose newly identified neurons were impaired, meaning they didn’t get the restorative sleep that normal mice did.
The mice that didn’t get their stress-induced sleep spent far more time in the dark, indicating they were more anxious and their stress hormone levels remained high.
Having found this new mechanism, the team now hopes to find ways to selectively target the responsible neurons to amplify their beneficial effects over sleep.
See also
The team was funded by the Wellcome Trust and the UK Dementia Research Institute. Being diagnosed with dementia can cause significant psychological distress, and the team hopes that if their research can lead to a way to boost the effects of sleep, it will also help people cope with a new diagnosis. People with dementia also suffer from greater emotional distress, and promoting REM sleep can also help reduce this burden.
About this news from sleep and psychology research
Author: Hayley Dunning
Source: Imperial College London
Contact: Hayley Dunning – Imperial College London
Picture: The image is attributed to Imperial College London
Original research: Closed access.
“A specific circuit in the midbrain senses stress and induces restful sleep” by Bill Wisden et al. Science
abstract
A special circuit in the midbrain recognizes stress and ensures restful sleep
Social stress (SDS), an ethological model of psychosocial stress, induces sleep in mice. Such sleep might enable resilience, but how stress promotes sleep is unclear.
Activity-dependent labeling revealed a subset of the ventral tegmental area γ-aminobutyric acid (GABA)-somatostatin (VTAVgat-Sst) cells that sense stress and drive non-rapid eye movement (NREM) and REM sleep by the lateral hypothalamus and also inhibit corticotropin-releasing factor (CRF) release in the paraventricular hypothalamus.
Temporary stress increases the activity of VTAVgat-Sst cells for several hours so that they can exert their sleep effect permanently. lesion of VTAVgat-Sst cells abolished SDS-induced sleep; without them, anxiety and corticosterone levels remained elevated after stress. A special circuit allows animals to restore mental and physical function through sleep, potentially offering a nifty way to treat anxiety disorders.
